Cannabinoids and Feeding: The Role of the Endogenous Cannabinoid System as a Trigger for Newborn Suckling

Transcription

1 Cannabinoids and Feeding: The Role of the Endogenous Cannabinoid System as a Trigger for Newborn Suckling Ester Fride SUMMARY. Cannabinoids are known to enhance appetite by activating cannabinoid (CB 1 ) receptors. This phenomenon is exploited to combat cachexia and loss of appetite in cancer and AIDS patients. The endocannabinoid 2-arachidonylglycerol (2-AG) is present in milk. Evidence is presented supporting a critical role for CB 1 receptors in survival of mouse pups. Thus neonates do not gain weight and die within the first week of life when their receptors are blocked. This is due apparently, to an inability to ingest maternal milk. This suggests that the endocannabinoid-cb 1 receptor system is unique in its absolute control over the initiation of the neonatal milk suckling response. It is further proposed that cannabis-based medicines should be developed to benefit infant failure to thrive. [Article copies available for a fee from The Haworth Document Delivery Service: HAWORTH. address: <getinfo@haworthpressinc. com> Website: < by The Haworth Press, Inc. All rights reserved.] Ester Fride, PhD, is Associate Professor, Department of Behavioral Sciences, and Head, Laboratory of Behavioral Biology, College of Judea and Samaria, Ariel, Israel This work was supported in part by a grant from the Danone Research Institute in Israel. [Haworth co-indexing entry note]: Cannabinoids and Feeding: The Role of the Endogenous Cannabinoid System as a Trigger for Newborn Suckling. Fride, Ester. Co-published simultaneously in Journal of Cannabis Therapeutics (The Haworth Integrative Healing Press, an imprint of The Haworth Press, Inc.) Vol. 2, No. 3/4, 2002, pp ; and: Women and Cannabis: Medicine, Science, and Sociology (ed: Ethan Russo, Melanie Dreher, and Mary Lynn Mathre) The Haworth Integrative Healing Press, an imprint of The Haworth Press, Inc., 2002, pp Single or multiple copies of this article are available for a fee from The Haworth Document Delivery Service [1-800-HAWORTH, 9:00 a.m. - 5:00 p.m. (EST). address: getinfo@ haworthpressinc.com] by The Haworth Press, Inc. All rights reserved. 49

2 50 Women and Cannabis: Medicine, Science, and Sociology KEYWORDS. Cannabinoids, endocannabinoids, feeding, appetite, nursing, suckling, neonatal ABBREVIATIONS. CB 1, cannabinoid 1, 2-AG, 2-arachidonylglycerol, CBD, cannabidiol Cannabis is well known appetite stimulant (Abel 1971; Mattes et al. 1994; Fride 2002a). It is possible that the enhancement of appetite is selective for snack foods (Foltin, Brady, and Fischman 1986; Mattes, Shaw, and Engelman 1994). A role of the endocannabinoid system in the primitive invertebrate, Hydra vulgaris, has been demonstrated (De Petrocellis et al. 1999), thus pointing at a very widespread stimulatory role for cannabinoids in feeding. This, for most cannabis users, undesirable side effect, has been clinically utilized for a number of years to combat a reduction in appetite and consequent weight reduction and wasting, as seen in conditions including AIDS and cancer (Mechoulam, Hanus, and Fride 1998). However, few controlled clinical studies have been performed (Bennett and Bennett 1999). In open pilot studies, dronabinol ( 9 -THC) caused weight gain in the majority of subjects (Plasse et al. 1991). A relatively low dose of dronabinol, 2.5 mg twice daily, enhanced appetite and stabilized body weight in AIDS patients suffering from anorexia (Beal et al. 1997) for at least 7 months. In another study on AIDS patients, no weight gain was reported over the course of 12 weeks of dronabinol administration (2.5 mg twice a day), whereas a dose of 750 mg/day of megestrol acetate (a synthetic progestational drug), effected significant weight gain (Timpone et al. 1999). In that study, a high dose of megestrol (with potential adverse effects including dyspnea and hypertension), and a low dose of dronabinol were used. Higher doses of dronabinol may be more effective, although side effects such as weakness, confusion, memory impairment and anxiety, are a concern. When dronabinol was administered to healthy volunteers, an increase in caloric intake was recorded after twice daily administrations for 3 days, when rectal suppositories were used, rather than the oral route (Mattes et al. 1994). When the effects of cannabis smoking by healthy volunteers on the intake of various types of food were compared, a selective increase in snack foods was observed (Foltin, Brady, and Fischman 1986). Thus the use of higher doses of cannabinoids as well as different routes of administration including the rectal (Bennett and Bennett 1999) or the sublingual (Whittle, Guy, and Robson 2001) route, should be further investigated. Studies in laboratory animals have confirmed the human data, and unequivocally shown that cannabinoid 1 (CB 1 ) receptors mediate cannabinoid-induced increase in food ingestion (Williams and Kirkham 2002), especially of palatable

3 Ester Fride 51 foods (Koch and Matthews 2001). Thus both exogenous cannabinoids ( 9 -THC) and the endocannabinoid anandamide-induced enhancement of appetite were reversed by the specific CB 1 antagonist SR141716A (Williams, Rogers, and Kirkham 1998; Williams and Kirkham 2002). SR141716A injected by itself reduced appetite and body weight. Whether palatability is required for the antagonist s anorectic effect is controversial (Colombo et al. 1998; Freedland, Poston, and Porrino 2000; Arnone et al. 1997). In a chronic study in mice, very low doses of anandamide (0.001 mg/kg) were effective in enhancing food intake (Hao et al. 2000), in according with a stimulatory effect of very low doses of anandamide in a series of cannabimimetic assays (Sulcova, Mechoulam, and Fride 1998). INTERACTIONS OF THE ENDOCANNABINOID SYSTEM WITH HORMONES REGULATING FOOD INTAKE CB 1 receptors have been located in the hypothalamus (Herkenham et al. 1991; Mailleux and Vanderhaeghen 1992), a brain structure which is important in weight regulation. Although the precise mechanism by which cannabinoid receptors enhance appetite and food intake is not known, progress has been made in recent years to uncover such mechanisms (Mechoulam and Fride 2001). Thus Arnone et al. (1997) showed that the neuropeptide Y (NPY)-induced increase in sucrose drinking was inhibited by SR141716A, possibly linking this hormone, which is known to enhance food intake (Mechoulam and Fride 2001), to cannabinoid-stimulated appetite. The hormone leptin is produced by fat tissue and is considered to be a key signal through which the hypothalamus senses the nutritional state of the body and helps maintain weight within a narrow range (Friedman 2000; Schwartz et al. 2000). Within the hypothalamus, the arcuate nucleus contains neurons with receptors for two appetite-stimulating peptides (neuropeptide Y and agouti-related protein), as well as receptors for two peptides that reduce appetite (α-melanocytestimulating hormone and cocaine-and-amphetamine-regulated transcript). Leptin directly suppresses the activity of the two appetite-stimulating peptides, and stimulates the activity of the appetite-reducing ones, thereby decreasing appetite. Other molecules indirectly affected by leptin include melanin-concentrating hormone and a family of neuropeptides called orexins, which enhance appetite, as well as corticotropin-releasing hormone and oxytocin, which cause mice to eat less and to lose weight. Di Marzo et al. (2001) have demonstrated that the endocannabinoid receptor system is an additional factor in this already complex weight-regulating system. Thus, when they administered leptin, the levels of the endocannabinoids anandamide and 2-arachidonylglycerol in the hypothalamus of normal rats were

4 52 Women and Cannabis: Medicine, Science, and Sociology reduced. Further evidence strengthens the idea that leptin down-regulates endocannabinoids. In a strain of obese rats in which leptin activity is impaired, the levels of endocannabinoids are higher than normal (Di Marzo et al. 2001). The same is true of obese ob/ob mice, which have an inherited lack of leptin, and of obese db/db mice, which have defective leptin receptors. Endocannabinoid levels are not affected in the cerebellum (which is commonly associated with motor coordination, but not with feeding) in these mice. Taking together the human and animal studies, the effects of the cannabinoid system on food intake and appetite are significant, representing one of a multitude of players involved in this vital function. ENDOCANNABINOIDS IN FOOD SUBSTANCES The discovery of anandamide in chocolate (di Tomaso, Beltramo, and Piomelli 1996) raised the possibility that endocannabinoids contribute to the attractiveness of, and perhaps the intense craving for, this desirable food. Indeed, orally administered endocannabinoids (anandamide and 2-AG), albeit in very high doses, induced cannabimimetic effects in mice (Di Marzo et al. 1998). The very low amounts of anandamide found in cocoa powder and even lower concentrations in unfermented cocoa beans, would suggest the possibility that the anandamide in chocolate may be an artifact of processing (Di Marzo et al. 1998). Anandamide congeners that do not bind CB 1 receptors, including linoleoyl ethanolamide, oleoyl ethanolamide and oleamide ( sleep factor, Cravatt et al. 1995), all display cannabiminetic effects when applied in vivo (Fride at al. 1997), probably by inhibiting the fatty acid amide hydrolase (FAAH) enzyme which breaks down anandamide (see Fride 2002a). Oleamide, when given orally, displayed cannabimimetic effects in mice at doses several magnitudes higher than those present in chocolate, similar to orally administered anandamide (Di Marzo et al. 1998). Taken together, these results suggest that anandamide in chocolate, whether present in cocoa beans, or as an artifact of processing, could be responsible for any cannabinoid contribution to chocolate craving. Future studies, testing anandamide and its congeners in more subtle behavioral assays such as drug discrimination or place preference designs may shed further light on the putative role for endocannabinoids in the rewarding effects of chocolate. Interestingly, in the same study, and in a more recent one, relatively high concentrations of the endocannabinoid 2-AG but very low quantities of anandamide were detected in various types of milk (for instance, 8.7 ± 2.8 µg 2-AG/g extracted lipids from mature human milk). These concentrations of 2-AG were much higher than those found in other foods such as soybeans, hazelnuts and oatmeal (Di Marzo et al. 1998; Fride et al. 2001a).

5 Ester Fride 53 DEVELOPMENTAL ASPECTS OF THE ENDOCANNABINOID-CB 1 RECEPTOR SYSTEM Based on the findings described above, it is suggested that, as 2-AG is found in milk in significant amounts, this endocannabinoid must be of importance for the development of the newborn mammal. Several observations on developmental aspects of the endocannabinoid system in the central nervous system support such a hypothesis. First, atypical distribution patterns of CB 1 receptors (i.e., a transient presence during development in regions where none are found at adulthood) were detected in white matter regions including the corpus callosum and anterior commissure (connecting neuronal pathways between the left and right hemispheres) between gestational day 21 and postnatal day 5, suggesting a role for endocannabinoids in brain development (Romero et al. 1997). Further, although initial reports studying the development of the cannabinoid receptor system during the first weeks of postnatal life in the rat described a gradual increase in brain CB 1 receptor mrna (McLaughlin and Abood 1993) and in the density of CB 1 receptors (Belue et al. 1995; Rodriguez de Fonseca et al. 1993), in later studies CB 1 receptor mrna was also detected from gestational day 11 in the rat (Buckley et al. 1998). Additional studies have uncovered more complex developmental patterns. Thus, whereas the highest levels of mrna expression of the CB 1 receptor are seen at adulthood in regions such as the caudate-putamen and the cerebellum, other areas such as the cerebral cortex, the hippocampus and the ventromedial hypothalamus display the highest mrna CB 1 receptor levels on the first postnatal day (Berrendero et al. 1999; Fernandez-Ruiz et al. 2000). Finally, endocannabinoids were also detected from the gestational period in rodents, 2-AG at 1000 fold higher concentrations than anandamide. Interestingly, while anandamide displayed a gradual increase, constant levels of 2-AG were measured throughout development except for a single a peak on the first postnatal day (Berrendero et al. 1999). Is it possible therefore, that the high levels of CB 1 receptor mrna and 2-AG which have been observed on the first day of life in structures including the hypothalamic ventromedial nucleus (which is associated with feeding behavior) comprise a major stimulus for the first episode of milk suckling in the newborn? BLOCKADE OF CB 1 RECEPTORS IN NEWBORN MICE Over the last few years, our group has investigated a role for the endocannabinoid system immediately after birth in mice. Administration of the specific CB 1 receptor antagonist SR141716A to the nursing mother had no effect on maternal weight, pup growth and development, or on maternal behavior (Fride,

6 54 Women and Cannabis: Medicine, Science, and Sociology Ginzburg and Mechoulam, unpublished observations). However, when CB 1 receptors were blocked by SR141716A in one day old pups by a single sc injection of SR141716A, a complete growth arrest and death within the first week of life was observed in virtually all SR141716A-treated pups (Fride et al. 2001a; Figure 1). This devastating effect of SR141716A on the pups was dose-dependent (between 5-20 mg/kg). Furthermore, for the complete (almost 100% mortality) effect to take place, the antagonist had to be injected within the first 24 hours of life. Co-administration of 9 -THC almost completely reversed the effect, thus strongly suggesting that the SR141716A-induced effects were CB 1 receptor mediated. Co-administration of the endocannabinoid 2-AG did not reverse the SR141716A-induced mortality, presumably due to its rapid breakdown. However, 2-AG injected together with its entourage (fatty acid-esters which are always co-released with 2-AG, but which do not bind CB 1 receptors, and which counteract the breakdown and reuptake of 2-AG; see Ben-Shabat et al. 1998), significantly antagonized the growth-arresting effects of SR141716A on the pups (Figure 2). Subsequent experiments designed to further support the specificity of the CB 1 receptor in the mediation of the antagonist-induced pup mortality indi- FIGURE 1. Five day old vehicle-injected (left) and SR141716A-injected (right) mouse pups. Pups, from the same litter, were injected sc (10 µl/g) within 24 hr after birth with vehicle (ethanol:emulphor:saline = 1:1:18), or SR141716A (20 mg/kg).

7 Ester Fride 55 cated that cannabidiol (CBD), the non-psychoactive, non-cb 1 receptor binding cannabinoid, did not reverse the effects of SR141716A (Fride et al. 2001a; Figure 2), while the CB 2 receptor antagonist, SR144528, did not affect pup growth (unpublished observations). MECHANISMS OF THE CB 1 RECEPTOR BLOCKADE-INDUCED GROWTH STUNTING EFFECTS An initial investigation of possible mechanisms involved in sequelae of CB 1 receptor blockade in pups suggested that maternal behavior toward SR141716A-injected pups was not adversely affected. On the contrary, the dams spent significantly more time licking and nursing the antagonist-treated pups (Fride et al. 2001a). Rather, the CB 1 receptor blockade on day 1 of life disables the ability of the newborns to initiate milk suckling, as their stomachs were empty of milk (Fride et al. 2001a). FIGURE 2. Summary of survival rates in pups one week after birth after various treatments on day 1 of life. SR1 = SR141716A (20 mg/kg), SR2 = SR (20 mg/kg), CBD = cannabidiol (20 mg/kg), Entourage = palmityl glycerol (5 mg/ kg) and lineoyl glycerol (10 mg/kg); these were added to the injection of 2-AG (1 mg/kg). LPA = lysophosphatidic acid (18:1, n-9, 20 mg/kg). All compounds were injected sc in the neck or flank in volumes of 10 µl/g. 100 %Survival 50 0 Vehicle SR1 SR2 CBD 2-AG+Entourage LPA THC+SR1 2-AG+Ent+SR1 CBD+SR1 LPA+SR1

8 56 Women and Cannabis: Medicine, Science, and Sociology More recent evidence for the role of CB 1 receptors in milk suckling is derived from CB 1 receptor-deficient (CB 1 2/2 knockout) mice, where it was observed that the CB 1 receptor antagonist had significantly less severe effects on the CB 1 2/2 pups, as compared to the effects on wild type mice (Fride et al., in preparation). Lysophosphatidic acid (LPA) is a multifunctional lipid mediator with growth factor-like properties. LPA occurs in brain in considerable concentrations and is structurally similar to the endocannabinoid 2-AG. The LPA and CB 1 receptors display substantial (30%) homology. LPA, with 2-arachidonic acid as the acyl moiety, differs only by the absence of a phosphate group from 2-AG while a related lysophosphatidic acid (with 1-arachidonic acid as the acyl moiety) has been detected in rat brain (Sugiura et al. 1999). A defective suckling response was reported in neonatal mice that have a targeted deletion of the gene for the LPA receptor (lp A1 ) (Contos et al. 2000). Our group therefore investigated the possibility that LPA and 2-AG may interact at their receptors. If the inhibition of milk ingestion in our experiments were due to an interaction of the CB 1 antagonist at the LPA receptor, or alternatively, if LPA interacts with the CB 1 receptor, then co-application of LPA with SR141716A on newborn pups should reverse the antagonist inhibition of pup development. This was not the case in our experiments. Thus, when LPA was co-injected with SR141716A, only a temporary delay in mortality, with borderline significance (p = 0.09), was observed (Fride, Rosenberg, and Mechoulam 2001b). Moreover, LPA did not bind to CB 1 receptors (Hanus and Fride, unpublished observations). Since the LPA employed contained oleic acid as the acyl moiety, and not arachidonic acid (which can not be obtained commercially), further investigation of the interaction between the LPA and CB 1 receptor systems is warranted. Several neuroactive substances have been implicated in milk suckling. For example, Smotherman and colleagues (Petrov, Varlinskaya, and Smotherman 1998) have demonstrated an inhibition of several components of the suckling response after injection of naloxone into the cerebral ventricles of rat pups. When effects of intracisternal injections of a specific µ opiate receptor antagonist on weight gain were recorded, only a slight, transient reduction was seen; similar injections into the cerebral ventricles did not have any effect on body weight (Petrov et al. 1998). Taken together, our studies argue for a critical role for CB 1 receptor activation in milk suckling in the newborn, presumably by 2-AG produced by the neonatal brain. As far as is known, the endocannabinoid-cb 1 receptor system is the first neural system discovered thus far that seems to display complete control over milk ingestion and neonatal survival.

9 Ester Fride 57 CONCLUSIONS Our data have indicated that the CB 1 receptor antagonist had to be injected within 24 hr after birth of mouse pups in order to produce a virtual 100% mortality effect (injection on day 2 resulted in less than 50% mortality). It is proposed that without CB 1 receptor activation by 2-AG (or another as yet undefined endocannabinoid) within the first 24 hr of life, the first suckling episode is not initiated. As the pups have not suckled yet, the source of this 2-AG must be the pup s brain, and not maternal milk. This is compatible with the surge of 2-AG and CB 1 receptor mrna in the 1-day old rat brain (Berrendero et al. 1999; Fernandez-Ruiz et al. 2000). The lower levels of 2-AG and CB 1 receptors present from day 2 onward are apparently too low, or too late, to allow the suckling response to be initiated on subsequent days. These observations further suggest that the enhancement in appetite and food intake induced by cannabinoids in the adult organism may only be the tip of the iceberg of the vital role for the cannabinoid system in milk suckling immediately after birth (Fride et al. 2001a). The comparatively more partial control of the endocannabinoid system of appetite and food intake by the mature organism should not diminish our efforts to develop cannabis-based medicines for appetite stimulation in conditions involving cachexia. Rather, it does suggest that treatment of children suffering such conditions may benefit at least as much as adults from cannabinoids to combat anorexia (Fride 2002b). Further, treating infants suffering from a failure to thrive with cannabinoid-derived medicines deserves future research. REFERENCES Abel, E.L Effects of marihuana on the solution of anagrams, memory and appetite. Nature 231(5300): Arnone, M., J. Maruani, F. Chaperon, M.H. Thiebot, M. Poncelet, P. Soubrie, and G. Le Fur Selective inhibition of sucrose and ethanol intake by SR , an antagonist of central cannabinoid (CB 1 ) receptors. Psychopharmacology (Berl) 132(1): Beal, J.E., R. Olson, L. Lefkowitz, L. Laubenstein, P. Bellman, B. Yangco, J.O. Morales, R. Murphy, W. Powderly, T.F. Plasse, K.W. Mosdell, and K.V. Shepard Long-term efficacy and safety of dronabinol for acquired immunodeficiency syndrome-associated anorexia. J Pain Symptom Manage 14(1):7-14. Belue, R.C., A.C. Howlett, T.M. Westlake, and D.E. Hutchings The ontogeny of cannabinoid receptors in the brain of postnatal and aging rats. Neurotoxicol Teratol 17(1): Bennett, W.A., and S.S. Bennett Marihuana for AIDS wasting. In Marihuana and Medicine, edited by G.G. Nahas, K.M. Sutin, D. Harvey, and S. Agurell. Totowa, NJ: Humana Press.

10 58 Women and Cannabis: Medicine, Science, and Sociology Ben-Shabat, S., E. Fride, T. Sheskin, T. Tamiri, M.H. Rhee,. Vogel, T. Bisogno, L. De Petrocellis, V. Di Marzo, and R. Mechoulam An entourage effect: Inactive endogenous fatty acid glycerol esters enhance 2-arachidonoyl-glycerol cannabinoid activity. Eur J Pharmacol 353(1): Berrendero, F., N. Sepe, J.A. Ramos, V. Di Marzo, and J.J. Fernandez-Ruiz Analysis of cannabinoid receptor binding and mrna expression and endogenous cannabinoid contents in the developing rat brain during late gestation and early postnatal period. Synapse 33(3): Buckley, N.E., S. Hansson, G. Harta, and E. Mezey Expression of the CB 1 and CB 2 receptor messenger RNAs during embryonic development in the rat. Neuroscience 82(4): Colombo, G., R. Agabio, G. Diaz, C. Lobina, R. Reali, and G. L. Gessa Appetite suppression and weight loss after the cannabinoid antagonist SR ife Sci 63(8):L Contos, J.J., N. Fukushima, J.A. Weiner, D. Kaushal, and J. Chun Requirement for the lpa1 lysophosphatidic acid receptor gene in normal suckling behavior. Proc Natl Acad Sci SA 97(24): De Petrocellis, L., D. Melck, T. Bisogno, A. Milone, and V. Di Marzo Finding of the endocannabinoid signalling system in Hydra, a very primitive organism: possible role in the feeding response. Neuroscience 92(1): Di Marzo, V., S.K. Goparaju, L. Wang, J. Liu, S. Batkai,. Jarai, F. Fezza, G.I. Miura, R.D. Palmiter, T. Sugiura, and G. Kunos Leptin-regulated endocannabinoids are involved in maintaining food intake. Nature 410(6830): Di Marzo, V., N. Sepe, L. De Petrocellis, A. Berger, G. Crozier, E. Fride, and R. Mechoulam Trick or treat from food endocannabinoids? Nature 396(6712): di Tomaso, E., M. Beltramo, and D. Piomelli Brain cannabinoids in chocolate. Nature 382(6593): Fernandez-Ruiz, J., F. Berrendero, M.L. Hernandez, and J.A. Ramos The endogenous cannabinoid system and brain development. Trends Neurosci 23(1): Foltin, R.W., J.V. Brady, and M.W. Fischman Behavioral analysis of marijuana effects on food intake in humans. Pharmacol Biochem Behav 25(3): Freedland, C.S., J.S. Poston, and L.J. Porrino Effects of SR141716A, a central cannabinoid receptor antagonist, on food-maintained responding. Pharmacol Biochem Behav 67(2): Fride, E. 2002a. Endocannabinoids in the central nervous system an overview. Prostaglandins, eu otrienes and Essential Fatty Acids in press. Fride, E. 2002b. Cannabinoids and cystic fibrosis: A novel approach to etiology and therapy. J Cannabis Therapeutics 2(1): Fride, E., Y. Ginzburg, A. Breuer, T. Bisogno, V. Di Marzo, and R. Mechoulam. 2001a. Critical role of the endogenous cannabinoid system in mouse pup suckling and growth. Eur J Pharmacol 419(2-3): Fride, E., E. Rosenberg, and R. Mechoulam. 2001b. Role of endocannabinoids in newborn food intake and development: interaction with lysophopspatidic acid? 2001 Symposium on the Cannabinoids, Burlington, ermont, International Cannabinoid Research Society 2001:100.

11 Ester Fride 59 Friedman, J.M Obesity in the new millennium. Nature 404(6778): Hao, S., Y. Avraham, R. Mechoulam, and E.M. Berry Low dose anandamide affects food intake, cognitive function, neurotransmitter and corticosterone levels in diet-restricted mice. Eur J Pharmacol 392(3): Herkenham, M., A.B. Lynn, M.R. Johnson, L.S. Melvin, B.R. de Costa, and K.C. Rice Characterization and localization of cannabinoid receptors in rat brain: a quantitative in vitro autoradiographic study. J Neurosci 11(2): Koch, J.E., and S.M. Matthews Delta9-tetrahydrocannabinol stimulates palatable food intake in Lewis rats: effects of peripheral and central administration. Nutr Neurosci 4(3): Mailleux, P., and J.J. Vanderhaeghen Distribution of neuronal cannabinoid receptor in the adult rat brain: a comparative receptor binding radioautography and in situ hybridization histochemistry. Neuroscience 48(3): Mattes, R.D., K. Engelman, L.M. Shaw, and M.A. Elsohly Cannabinoids and appetite stimulation. Pharmacol Biochem Behav 49(1): Mattes, R.D., L.M. Shaw, and K. Engelman Effects of cannabinoids (marijuana) on taste intensity and hedonic ratings and salivary flow of adults. Chem Senses 19(2): McLaughlin, C.R., and M.E. Abood Developmental expression of cannabinoid receptor mrna. Brain Res Dev Brain Res 76(1):75-8. Mechoulam, R., and E. Fride Physiology. A hunger for cannabinoids. Nature 410(6830):763, 765. Mechoulam, R., L. Hanus, and E. Fride Towards cannabinoid drugs revisited. Prog Med Chem 35: Petrov, E.S., E.I. Varlinskaya, L.A. Becker, and W.P. Smotherman Endogenous mu opioid systems and suckling in the neonatal rat. Physiol Behav 65(3): Petrov, E.S., E.I. Varlinskaya, and W.P. Smotherman Endogenous opioids and the first suckling episode in the rat. Dev Psychobiol 33(2): Plasse, T.F., R.W. Gorter, S.H. Krasnow, M. Lane, K.V. Shepard, and R.G. Wadleigh Recent clinical experience with dronabinol. Pharmacol Biochem Behav 40(3): Rodriguez de Fonseca, F., J.A. Ramos, A. Bonnin, and J.J. Fernandez-Ruiz Presence of cannabinoid binding sites in the brain from early postnatal ages. Neuroreport 4(2): Romero, J., E. Garcia-Palomero, F. Berrendero, L. Garcia-Gil, M.L. Hernandez, J.A. Ramos, and J.J. Fernandez-Ruiz Atypical location of cannabinoid receptors in white matter areas during rat brain development. Synapse 26(3): Schwartz, M.W., S.C. Woods, D. Porte, Jr., R.J. Seeley, and D.G. Baskin Central nervous system control of food intake. Nature 404(6778): Sugiura, T., S. Nakane, S. Kishimoto, K. Waku, Y. Yoshioka, A. Tokumura, and D.J. Hanahan Occurrence of lysophosphatidic acid and its alkyl ether-linked analog in rat brain and comparison of their biological activities toward cultured neural cells. Biochim Biophys Acta 1440(2-3): Sulcova, E., R. Mechoulam, and E. Fride Biphasic effects of anandamide. Pharmacol Biochem Behav 59(2):

12 60 Women and Cannabis: Medicine, Science, and Sociology Timpone, J.G., D.J. Wright, N. Li, M.J. Egorin, M.E. Enama, J. Mayers, and G. Galetto The safety and pharmacokinetics of single-agent and combination therapy with megestrol acetate and dronabinol for the treatment of HIV wasting syndrome. In Marihuana and Medicine, edited by G.G. Nahas, K.M. Sutin, D. Harvey, and S. Agurell. Totowa, NJ: Humana Press. Whittle, B.A., G.W. Guy, and P. Robson Prospects for new cannabis-based prescription medicines. J Cannabis Therapeutics 1(3-4): Williams, C.M., and T.C. Kirkham Reversal of delta 9-THC hyperphagia by SR and naloxone but not dexfenfluramine. Pharmacol Biochem Behav 71(1-2): Williams, C.M., P.J. Rogers, and T.C. Kirkham Hyperphagia in pre-fed rats following oral delta9-thc. Physiol Behav 65(2):343-6.